Multi-mode mobile devices can support and connect to multiple radio access technologies simultaneously. Examples of radio access technologies include, but are not limited to Global System for Mobile Communication (GSM), Code Division Multiple Access (CDMA), Universal Mobile Telecommunication System (UMTS)/Wideband Code Division Multiple Access (WCDMA), CDMA2000 1x and 1xEV-DO, Long Term Evolution (LTE), Long Term Evolution-Advanced (LTE-A), among others. In addition to these radio access technologies which operate on licensed spectrum and are typically known as cellular radio access technologies, a multi-mode mobile device may support variants of IEEE 802.x-based radio access technologies such as WiFi, WiMAX, and provide Wireless Local Area Network (WLAN) service on unlicensed spectrum. A multi-mode mobile device may also communicate through short range wired or wireless communications such as IrDA, Bluetooth™, near field communications (NFC), Universal Serial Bus (USB), amongst others. Moreover, a multi-mode mobile device capable of supporting Unlicensed Mobile Access (UMA) can roam and handover between cellular and WLAN radio access technologies.
When a multi-mode mobile device is in a coverage area of multiple radio access networks, the mobile device may register with more than one, provided that the corresponding radio access technology at the device is turned on and active. Current radio technology standards require the multi-mode mobile device to monitor all of the radio access networks to which it is registered.
As used herein, a multi-mode mobile device that is not performing an active data transfer is said to be operating in IDLE mode. In IDLE mode, the device performs discontinuous reception (DRX) where it periodically turns on its receiver to listen for possible “paging”, “beacon”, or similar messages indicating the presence of incoming voice or data calls. When not listening for incoming calls, the device deactivates its receiver to conserve battery life. The use of the term IDLE in the present disclosure includes states in certain radio access technologies that are considered connected, such as within UMTS when the device is in a Cell_PCH or URA_PCH state.
With the evolution in wireless technology, services such as voice, short message service (SMS), emergency call, and/or other applications may all be supported by different radio access technologies. It is possible that a multi-mode mobile device may be able to obtain all the subscribed services from one or more radio access technologies to which the mobile device is capable of connecting. However, a multi-mode mobile device is still required to wake up periodically to listen to paging/beacon messages from all the radio access networks to which it is registered. This monitoring of multiple networks decreases the already limited battery life of a multi-mode mobile device.